A student finds the melting point of an organic solid in the literature to be re

Question

A student finds the melting point of an organic solid in the literature to be recorded as 114 degree C. The student observes that the solid begins melt 112 degree C and finishes melting at 114 degree C. What experimental melting point should the student record? Indicate the best answer with an X 112 degree C. 113 degree C. 114 degree C. 112-114 degree C Another student takes the melting point of the same compound of problem 7. The melting temperature begins at 120 degree C and ends at 125 degree C. What is the likely reason for the high Indicate the best answer with an X. The thermometer is not calibrated, causing the temperature to appear higher than it is. The rheostat is set too high, causing the temperature to rise too fast through the melting zone The sample contains an impurity, causing the sample to appear to melt at a higher temperature. The rheostat is set too low, causing the temperature to dwell in the melting zone. How does the order of melting of the pentane isomers (pentane, 2-methylbutane and 2, 2- dimethylpropane) compare theoretically to their order of boiling? You are given two compounds, one of which is known to be urea, which melts at 132-3 degree C. Which of the following techniques is the best way to determine which compound is urea? Indicate the best answer with an X. Add urea to each sample and melt them. The melting temperature remains the same is urea, and the one that goes up is the other compound. Add urea to each sample and melt them. The one whose melting temperature remains the same is urea, and the one that goes down is the other compound Melt the compounds separately, and the one that melts at 132-3 degree C is urea. Melt the compounds at the same time, the one that melts nearest to 132.3 degree C is urea.

Explanation / Answer

7) 112 - 114 C

Experimental melting points should always be reported as range. here melting starts from 112 and ends at 114 C so we should report it as 112 - 114 C

8) rheostat is set too low causing the temperature to dwell in the melting zone

otherwise there is no possible way showing higher melting point as the presence of impurities will make the melting point to decrease and if rheostat is set too high then it will show the melting point at lower temperature

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